Method of and means for classifying and separating suspended solids



April ,18, 1939. SHEPHERD 2,154,779

METHOD OF AND MEANS FOR CLASSIFYING AND SEPARATING SUSPENDED SOLIDSFiled Feb. 24, 1937 2 Sheets-Sheet l mwboifm T. L. SHEPHERD April 18,1939.

METHOD OF AND MEANS FOR GLASSIFYING AND SEPARATING SUSPENDED SOLIDSFiled Feb. 24, 1937 2 Sheets-Sheet 2 Patented Apr. 18, 1939 UNITEDSTATES PATENT OFFICE METHOD OF AND MEANS FOR CLASSIFY- ING AND SOLIDSSEPARATING SUSPENDED 6 Claims.

My invention relates to improvements in method of and apparatus forclassifying and separating suspended solids, and more particularly to amethod and apparatus for such purpose utilizing coordinated, centrifugalforces, amalgamation and electro-chemical action.

The primary object of my invention is to provide a method of andapparatus for classifying and separating suspended solids which is ofsimple procedure and embodiment, which permits of continuous operation,and therein maximum recovery of classes of solids is effected.

Another object is to provide a method and apparatus, of the characterdescribed, wherein centrifugal force is employed for classification andseparation, but without the use of any moving parts as customarilyemployed in centrifugal processes and apparatus employed for suchpurposes.

A further object is to provide a method and apparatus, as described,wherein the application of centrifugal force to the treated pulp is afunction of pulp stream velocity, therefore providing for an extremelyhigh capacity in terms of pulp treated per area of flow circuit.

Another object is to provide, in a method and apparatus as described,electro-chemical treatment of pulp and mercury such as to promoterecovery of highly dispersed noble metals, including gold, byamalgamation, and to preclude fouling of the mercury with consequentmercury loss.

Other objects, the advantages and uses of the invention will becomeapparent after reading the following specification and claims, and afterconsideration of the drawings forming a part of the specification,wherein:

Fig. l is a vertical sectional view of an apparatus embodying featuresof my invention;

Fig. 2 is a top plan view of the apparatus illus-- trated in Fig. 1,parts thereof being broken away;

Fig. 3 is a flow diagram illustrating use of the apparatus of Fig. 1 incarrying out the method of my invention; and

Fig. 4 is a schematic view of a modified form 5 of the apparatus of Fig.1.

I have selected for the purpose of this specification, an embodiment ofmy invention particularly suitable for the classification and separationof values from the ore pulp of precious metals, such as that containingsuspended gold, platinum and silver, although it will be at onceapparent that suspended solids of other character may be classified andrecovered by obvious application of the procedure and apparatus hereindescribed.

In general, my invention contemplates the feeding of a pulp streamcontaining the suspended solids, as from a pump A under pressure throughan annular series of jets B which direct their streams tangentiallyoutwardly into an annular pool of mercury C, thus imparting bodilywhirling movement to the mercury pool and a similar whirling movement tothe pulp stream. This whirling movement of the pulp stream causes eachof its suspended solid components to react under centrifugal force indegrees proportional to the specific gravity of each such component. Theheaviest particles, for example, gold and platinum, will assume aposition at the radially outermost portion of the mercury chamber, sincesuch metals have a greater specific gravity than mercury.

Those components of the pulp suspensions which are lower than mercury inspecific gravity and which do not amalgamate with mercury will be forcedupwardly with the carrier fluid of the pulp through the pool C and intoan area D affording classification of the lighter particles. In itstravel to the area D, for further classification, the pulp stream, whichis still in whirling motion because of the jets B, is diverted radiallyinwardly, thus to increase its velocity. Under such increased velocityof both upward flow and rotational movement, the pulp is admitted to anannular recess E extending radially outwardly from the normal streamfiow which recess is provided with tangential outlets F through itsoutermost wall arranged to carry away the heavier of the suspendedsolids which were incapable of remaining in the pool of denser mercury.

Two or more of the recesses or chambers E may be used as requirementsmay dictate instead of but one, and arranged, for example, as shown inFig. 4.

Provision is made for subjecting the pulp stream electrically to adifference in potential as between the jets B and the mercury chamber,thus to nullify the effect of the Brownian movement on colloidalsuspensoids which may otherwise remain too widely disposed in the pulpfluid to admit of separation. Such electrical current Will also aid inkeeping the mercury fresh and amenable to amalgamation.

With reference to Figs. 1 and 2, the apparatus illustrated therein maycomprise an outer shell including a lower section 2 within which themercury pool C is retained, and an upper section 3, within which theannular recess E is located, the upper portion 4 thereof being taperedinwardly to a central vertically aligned outlet 5. Located within theouter shell is an inner shell 6 having a substantially vertical sidewall terminating at its upper end in a closed conical portion 7 ofslightly greater pitch than the surrounding wall of the outer shellsection 4. The inner shell is closed at its lower end by a sump 8secured to the shell 6 by bolts 9 which pass through the section 2 butwhich are insulated therefrom as is the sump, by suitable insulatingmaterial II.

I prefer to construct the lower section 2 of the outer shell in twoparts I 2 and I3, thus to facilitate machining, and to tie these partstogether and with the upper'section 3 by tie rods [4, which may extendthrough suitable flanges formed on the parts l2 and I3 and section 3respectively. In order that the lower section 2 of the outer shell maybe electrically insulated I from the upper section 3, and from the innershell,

suitable insulation material I may be interposed between the part l2 andsection 3 of the outer shell and similar material [5 placed between thetie rods I l and the flanges of the shell elements 3, l2 and I3,respectively. The jets B being formed also of insulating material, in amanner hereinafter described, the section 2 is therefore electricallyinsulated from the inner shell 6. An inlet pipe i! may be connecteddirectly to the sump 8 and an outlet pipe l8 to the outlet 5 of theouter shell, as shown.

With reference to Fig. 2, the jets B may be formed by cutting orotherwise providing radially directed curved grooves 2| in the opposedfaces of two rings 22 of such material as hard rubber, and in placingthe rings face to face between the adjacent surfaces 23 and 24 of theinner shell 6 and outer shell portion l3, as shown. The bolts 9 serve tolock the jet assembly firmly in place. For purpose of illustration, Ihave shown the section of the jet assembly at the right of Fig. 1 asfollowing the curved axis of the grooves 2|.

Referring now to Fig. 1, the contour of the inner walls of the lowershell section 2 formed of the parts l2 and I3 is such that the mercurypool C retained therein may move outwardly under centrifugal force asduring whirling movement under influence of the pulp streams withoutbeing displaced therefrom, and without breaking immersion of the jetrings 22 therein. Travel of the pulp after passing through the mercurypool C must be upward and radially inward by virtue of the recedingwalls 26 and 21 on the part l2 and shell 6, as shown, thus to increasethe velocity of the whirling pulp stream as it approaches theclassification zone of the apparatus. 7

In practice, I prefer to establish an electrical circuit between theincoming pulp stream from the jets B and the mercury pool 0, and forthis purpose the sump 8 and outer shell section 2 may be connected to analternating current line 28 by suitable conductors, as shown at 29 and30. For most installations, a voltage of 110 at a frequency suitable forincandescent lighting is sufficient, although certain pulps may requirehigher voltages because of a deficiency of soluble salts. The current soapplied, I have found, also has a desirable effect in minimizing mercuryfouling, as from inorganic substances.

In operation the pulp, after proper dilution, is admitted from the pumpA under pressure to the inner shell 6 by entry through the inlet pipeIT. The closed upper portion of the inner shell functions as a pressureequalizer, after the manner of an air cushion, thus to compensate for Vouter shell section 2.

pump surging or change in head where hydrostatic head is used in placeof the pump A.

. Such pulp, under substantially uniform pressure may pass from withinthe shell 6 through the jets B and directly into the mercury pool 0which, because of the tangential feed from the jets and the pressure atwhich the pulp is so admitted, is caused to rotate bodily, accompaniedby a whirling motion of the pulp stream. As heretofore pointed out, theeffect of centrifugal force acting alike on pulp stream and mercury willbe to cause the pulp suspensions, which have a specific gravity greaterthan mercury, to pass directly through the mercury pool C and radiallyoutwardly to, the inner wall of the If the suspension is gold,amalgamation may'likewise take place, but in any event, such suspensionwill be separated from the carrier fiuid of the pulp and retained withthe mercury in the section 2.

During this stage of the process, smaller particles which are capable ofamalgamation, but which may otherwise be difiicult to recover, becauseof colloidal dispersion, will form an amalgam with the mercury, suchcondition being induced in part by the eifect of the difference inpotential between the pulp as it leaves the jet and the mercury,provided by the electrical circuit described, and in part because of theforce with which the pulp is caused to enter the body of mercury atapoint beneath the surface thereof. Such latter effect I have found to bemany times more effective than mere surface to surface contact as widelypracticed in present day amalgamating devices, such for example, asamalgam tables, revolving amalgaming devices and the like.

It is not without reason to assume, however,

that some values of a lighter nature may successfully avoid entrapmentwithin the lower section 2, and this may be particularly true ofincluded values, the whole mass of which presents a specific gravityless than mercury. For the classification and separation of such values,I have provided the upper section of the apparatus with the radiallyextending annular recess E in the inner wall of the section 3 at a pointwhere the velocity of the whirling pump stream 7 is increased in themanner heretofore explained. Suitable outlet pipes 32 communicating withthe outermost portion of the recess E serve to conduct away the heaviersuspensions of the suspended solids which have passed above the mercurychamber and in this manner further classification and separation iscarried out.

The latter classification of the suspended solids, together with theirseparation from the pulp, may be multiplied and made effective forsucceedingly lighter ends by providing additional recesses E, asindicated at E, in Fig. 4.

Having thus illustrated and described specific embodiments of myinvention as applicable to the art of the recovery of noble metals fromore pulp, it will be understood that the process and apparatus of myinvention may be applied with equal success to the recovery of suspendedsolids of other substances, and that a liquid other than mercury, butheavier than the carrier liquid of the pulp, may be used for therecovery of relatively light suspensions.

I claim:

1. In an apparatus of the character described, means providing anannular chamber located in a substantially horizontal plane, mercury insaid chamber to form an annular pool free to rotate bodily about theaxis of said chamber, a plurality of nozzles having their outletorifices submerged in said mercury and positioned in such manner as toadmit fiuid pulp, passing therethrough under pressure, into the mercuryat the inner radial portion of the pool and spaced away from the bottomwall of said chamber and at an angle to induce bodily rotation of thepool, whereby suspensions contained in said pulp are caused to moveradially outwardly through the mercury under centrifugal force inrelation to the specific gravities of the suspensions and the mercury,means providing an annular classifier chamber in vertical alignment withsaid mercury chamber, ducts extending tangentially away from the outerregion of said classifier chamber, and means for conducting the fluidpulp from said mercury chamber while still in whirling motion upwardlyinto said classifier chamber.

2. In an apparatus for separating metals from a fluid ore pulp byamalgamation, a chamber for confining a. pool of mercury, a nozzleprojecting into said chamber and having its outlet at a point below themercury level of said chamber, said nozzle having all of that portionthereof extending into said chamber and beneath the mercury level formedof a dielectric material, means for feeding fiuid pulp under pressure tosaid nozzle, said chamber providing an electrode surface of a contactingmercury contained therein, and means providing an electrode surface forcontacting said pulp prior to its admittance to said nozzle.

3. In an ore separating apparatus, means forming an annular chamberhaving a maximum diameter in its lower region and tapering conicallyupwardly and inwardly to a discharge zone, an annular pool of mercury insaid lower region, and means for injecting a suspension of ore pulp, oflesser average specific gravity than mercury, spirally outwardly intothe inner region of said pool at points spaced radially a greaterdistance from the axis of said chamber than said discharge zone, wherebyto cause said pulp to rotate inside said pool and thence to spiralupwardly and inwardly, and the heavier values to pass radially outwardlythrough said pool and be collected in said lower region of the chamber.

4. In an ore separating apparatus, means forming an annular chamberhaving a maximum diameter in its lower region and tapering conicallyupwardly and inwardly to a discharge zone, an annular pool of mercury insaid lower region, and means for injecting a suspension of ore pulp, oflesser average specific gravity than mercury, spirally outwardly intothe inner region of said pool at points spaced above the bottom of saidpool, whereby to cause said pulp to rotate inside said pool and thenceto spiral upwardly and inwardly, and the heavier values to pass radiallyoutwardly through said pool and to be collected in said lower region ofthe chamber.

5. In an ore separating apparatus, a series. of nozzles directedsubstantially tangentially outwardly, means forming an annular chamberhaving a lower region into which said nozzles are arranged to dischargehorizontally, and having a conical region extending upwardly andinwardly to a zone of smaller radius than that of the discharge ends ofsaid nozzles, an annular pool of mercury in said lower region, and meansfor supplying to said nozzles a suspension of ore pulp having an averagelesser specific gravity than mercury.

6. In an ore separating apparatus, means forming an annular chamberhaving a toroidal lower region and an upwardly contracting conical upperregion, an annular pool of mercury in said lower region, and means forinjecting into said mercury pool, at substantially the center of saidtoroidal region, a plurality of outwardly spiralling, substantiallyhorizontal jets of ore pulp suspension adapted to be directed upwardlyby said mercury pool.

THOMAS LAMBERT SHEPHERD.

